The force exerted on a cylindrical intruder as it penetrates a granular medium was analyzed utilizing both experiments and the discrete element method (DEM). In this work, a series of penetration experiments were performed, considering cylindrical intruders with different nose shapes. We found that the drag force of the intruder with a hemispherical nose is close to that of those with conical noses with apex angles of 53° and 90°. The drag force of the blunt-nosed intruder is bigger; the drag force of the conical-nosed intruder with an apex angle of 37° is the smallest. We studied the interplay between the drag force on an intruder with a hemispherical nose and key variables—the penetration velocity (V), penetrator’s diameter ($d_{\mathrm{i}}$), and friction coefficient (μ). From this analysis, two piecewise functions were derived: one for the average drag force versus the penetration velocity, and the other for the scaled drag force versus the friction coefficient. Furthermore, the average drag force per contact point, F_a/P, can be succinctly represented by two linear relationships: F_a/P = 0.232$\mu$ + 0.015(N) for $\mu <0.9$, and F_a/P = 0.225(N) for $\mu \ge 0.9$.

In this paper, the effect of rotational resistance on particle motion in discrete element method is studied. In the discrete element method, the interaction between particles is simulated by point contact, and the mechanical constitutive model of contact action is established by a set of normal and tangential springs and dampers for each contact point. However, in the process of contact between particles, there are not only the normal and tangential forces that affect the relative translation of particles, but also the torque effect that affects the mutual rotation of particles. In this paper, the effect of rotating resistance on particle motion is studied by adding rotating spring and rotating damper to the contact point model. The rolling process of a single sphere and the formation process of a three-dimensional particle pile under certain conditions are simulated, and some results are obtained which are different from those without considering the rotation resistance. These results have some guiding significance for the motion behavior of granular materials in nature and engineering.